1. Field of the Invention
The present invention relates to a bending device mainly for bending a slender, long pipe three-dimensionally.
2. Related Art
In an ordinary bending device of this kind of the prior art, a pipe to be worked is rotated on its axis by a twisting unit holding the pipe at a proper portion, to set a bending direction, and is bend in the set position by one or two bending units which are arranged at one or two sides of the twisting unit.
Since, however, the aforementioned pipe bending device of the prior art is constructed such that the pipe is rotated on its axis by the twisting unit, the already bent leading end portion is twisted while being sequentially bent from the leading end portion, to raise a defect that a thin, longer pipe is deformed in the shape of its bent portion. Thus, the conventional pipe bending device has a tendency to be applied exclusively to a relatively large, thick and short pipe and is accordingly troubled by having its working range limited.
Since, moreover, the twisting unit is fixed in position, nothing but a remarkably short pipe can inconveniently be worked, unless the chucking position of the twisting unit relative to the pipe is changed each time it is not located at the center of the pipe.
In order to solve this problem, we have proposed a pipe bending device (as in Japanese Patent Laid-Open No. 93029/1987), which is equipped with: a chuck unit for gripping a pipe of a straight shape at its arbitrary portion; and a bending unit so disposed on at least one of the righthand and lefthand sides of the chuck unit as to move back and forth. The bending unit includes: a support member formed in its top with a pipe setting guide; a rotary member so mounted on the support member and formed in its wall with a guide groove similar to that of the support member as to rotate over the range of 360 degrees in a direction perpendicular to the axis of the pipe; and a motor-driven roller type bending unit mounted on the rotary member. The bending direction of the pipe can be set by rotating the roller type bending unit through the rotary member.
Since, however, this pipe bending device has a bending motor arranged in the roller type bending unit, this unit has its weight and capacity enlarged to increase the load upon a twisting motor for rotating the roller type bending unit and a drive motor for a movable unit for moving a moving unit. Due to a large weight (or mass), moreover, not only the accuracy is deteriorated due to the fine vibration which is generated in the upper portion of a support member, but also a stop time period is required till the attenuation of the vibration. Still moreover, the individual portions are required to have rigidity, and the moving speed and twisting rate are lowered. Furthermore, a certain limit is exerted upon the bending shape of the pipe. Furthermore, the power wires of the bending motor and the signal wires for locating the position are liable to be broken thereby to damage the device.